1. Field
Embodiments of the invention generally relate to processes for fabricating electronic devices on substrates, and more specifically, to monitoring process parameters in an electronic device fabrication process.
2. Description of the Related Art
The demand for faster, more powerful integrated circuit (IC) devices has introduced new challenges for IC fabrication technology, including the need to etch high aspect ratio of features such as trenches or vias on a substrate, such as a semiconductor wafer. For example, deep trench storage structures used in some dynamic random access memory applications require deep high aspect ratio trenches etched into a semiconductor substrate. Deep silicone trench etching is typically carried out in a reactive ion etching (RIE) process utilizing a silicon oxide mask.
Conventional systems which have shown robust performance in etching high aspect ratio features in semiconductor wafers is the APPLIED CENTURA HART™ Etch System and the Decoupled Plasma Source (DPS®) system available from Applied Materials, Inc. located in Santa Clara, Calif. The HART™ etching system utilizes a MERIE reactor capable of etching trenches having aspect ratios up to 70:1 while maintaining trench depth uniformity of 5 percent from center to edge. However, in order to enable fabrication of integrated circuits having sub-90 nm critical dimensions, circuit designers have demanded improved trench uniformity at even higher aspect ratios. Thus, it would be desirable to improve etching performance to enable the realization of next generation devices.
In order to meet these challenges, improvements must be made in monitoring process parameters on the wafer, such as wafer temperature and feature depths or dimensions, during processing. Generally, conventional measurement techniques and devices include thermocouples or probes positioned in proximity to the wafer, such as pyrometers or other probes to monitor wafer temperature. Other conventional measurement techniques include scatterometry, optical emission spectroscopy, laser inferometry, and the like, or a conventional determination in the time domain and/or frequency domain to facilitate an endpoint for an etch process. While these conventional processes may, in some instances, provide useful results, the ever-increasing trench depths, aspect ratios, and critical dimensions may leave the conventional measurement processes lacking for next generation processes.
Therefore, there is a need for an improved apparatus and method for providing an accurate and real-time metric of processing parameters.